Such test tube holder inserts are known. A cross-sectional view of such a known test tube holder insert is shown in FIG. 1 on the appended drawing. The insert shown comprises a ring 1 which in a manner not shown in any greater detail, is designed to be snapped in place in any of the holes in a tray provided with holes for receiving test tubes and belonging to a not shown test tube rack. In the embodiment shown, the ring 1 is provided with spring members in the form of resilient tongues 2, which extend obliquely towards the centre axis of the ring 1.
It has, however, been found that an insert designed in this manner, does not ensure that the test tubes in fact stand vertically in the test tube rack. This is particularly important in order to avoid spillage in connection with e.g. automatic pipetting of radioactive or other toxic liquids in certain applications.
Test tube racks having two trays provided with holes and arranged above each other with the holes aligned for receiving test tubes, are also known. In such test tube racks, inserts of the kind shown in FIG. 1, are secured in the holes in both trays. Hereby, a more stable but not completely reliable fixation is obtained of the lower portion of the test tubes since, after all, the test tubes can end askew.